In preparing an asphalt road, the hot asphalt is placed on the roadway by a "paver" which moves along as it spreads the asphalt. The asphalt must then be rolled while it may still be compacted, that is, before it has become too cool. Generally, with a single roll compactor several passes over each section are required toward and away from the paver. A heavy dual roll compactor can provide the required compaction of each area with a single pass toward the paver and a return pass.
Vibrating the rolls of a single or dual roll compactor is especially effective in its compacting effect. However, the vibration must be adjusted so that it also is not over-effective and does not leave roll marks in the asphalt surface.
It is the practice only to start the vibration after the compactor has started its travel and also to reverse the rotation of the eccentric weights when the direction of travel is reversed. Ideally, the first roll over the asphalt should be with only the required vibration and each successive roll should vibrate with a successively higher frequency. With a dual roll compactor there are four such rolls in the two passes mentioned. Their respective adjustments for each pass and such a sequence have heretofore not been provided for. As one complication, it should be mentioned that one side of the compactor is preferably provided with a minimum of overhang so that the machine can reach and compact to one edge of the roadway and then to the other edge as well by reversing the machine respecting the location of the paver. Such a reversal would require reversing whatever adjustments have been made.
The object of the present invention is to provide a frequency sequence selection which may be also reversed when the machine is reversed.